The marking of steel blocks with certain characters is useful, for example, in a rolling mill in which hot slabs are to be differently processed and are therefore to be visibly distinguished from one another.
A conventional way of marking such a hot steel body, e.g. as described in German Pat. No. 2 728 058, involves the embossing of symbols in a face of that block with the aid of a punch. Such a procedure, however, becomes cumbersome and uneconomical with symbols higher than about 25 mm. In practice it is frequently necessary to use characters of a height between about 6 and 25 cm in order to enable their recognition at greater distances from, for example, the operator's position on a crane serving to manipulate hot slabs or the like.
It has also been proposed (see German published specification No. 27 20 330) to guide a working head linearly along a surface to which such symbols are to be applied, this head being provided with a suitable marker designed to write the desired characters in succession on that surface. However, the usual type of marker such as a paint brush would not be suitable for writing on a hot slab since the dyes employed would immediately char at a temperature of, say, 500.degree. C. The marking operation would therefore have to be delayed until the slabs have been cooled sufficiently, at which time they may no longer be precisely identifiable as to their destination. Moreover, these dyes are liable to be washed out on a surface exposed to the weather.
For a completely different purpose, namely the coating of large surfaces of metallic articles with layers of other metals, it is known to heat an article to be coated to a temperature of at most 200.degree. C. and to spray that surface with the aid of a nozzle through which a wire of coating material is continuously fed from behind for atomization of its leading end at the nozzle outlet. That technique is described in Bulletin 244 of the firm Metco Ltd. in Chobham, United Kingdom, headed "Metco New Type 5 K Heavy Duty Metallizing Machine". A spray head suitable for this purpose is shown on page 147 of Volume 2 of a book titled The Way Things Work, published 1971 by Simon and Schuster, New York. Conceivably, such a metallic spray could be directed through a suitable mask onto a face of a steel body to form characters thereon, yet I am not aware of any prior proposal of this nature.